Warning when Joining on two columns with different datatypes

[moalk101]

So I had an issue with innerjoin. When joining two DataFrames where the columns specified in on= :c1 => :c2 have different datatypes but the same values(one is a string and the other is of type Int64), the result is always an empty DataFrame. It took me a while until I figured it out.
Is it possible to build in a Warning or an Error when joining on Columns with different DataTypes?
Example:

julia> df1 = DataFrame(
           Age = ["25", "30", "35"],
           C11 = [50000.0, 60000.0, 70000.0]
       )

3×2 DataFrame
 Row │ Age     C11     
     │ String  Float64 
─────┼─────────────────
   1 │ 25      50000.0
   2 │ 30      60000.0
   3 │ 35      70000.0

julia> df2 = DataFrame(
            Age = [25, 30, 35],
             C22 = [50000.0, 60000.0, 70000.0]
       )

3×2 DataFrame
 Row │ Age    C22     
     │ Int64  Float64 
─────┼────────────────
   1 │    25  50000.0
   2 │    30  60000.0
   3 │    35  70000.0

julia> innerjoin(df2,df1,on= :Age => :Age)
0×3 DataFrame
 Row │ Age    C22      C11     
     │ Int64  Float64  Float64 
─────┴─────────────────────────

Thank you in advance!

[bkamins]

We cannot add this warning, since it if quite common to have columns of element type Any, which can store anything. Unfortunately, from Julia's perspective number 1 and string "1" are just two different values.